undici vulnerable to downstream response splitting via retry interceptor
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Partial Red Hat: 1 fixed, 17 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
Summary
undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| NodeJS | undici | before 6.28.1; 7.0.0 to before 7.29.1; 8.0.0 to before 8.10.2 | 6.28.1, 7.29.1, 8.10.2 | Patch available | CNA |
| — | undici (npm) | before 6.28.1 | 6.28.1 | Patch available | GHSA-r53p-7pc4-xj5r |
| — | undici (npm) | 7.0.0 to before 7.29.1 | 7.29.1 | Patch available | GHSA-r53p-7pc4-xj5r |
| — | undici (npm) | 8.0.0 to before 8.10.2 | 8.10.2 | Patch available | GHSA-r53p-7pc4-xj5r |
- undici VendorNodeJS Affected before 6.28.1; 7.0.0 to before 7.29.1; 8.0.0 to before 8.10.2 Fixed in 6.28.1, 7.29.1, 8.10.2 Patch available CNA
- undici (npm) Vendor— Affected before 6.28.1 Fixed in 6.28.1 Patch available GHSA-r53p-7pc4-xj5r
- undici (npm) Vendor— Affected 7.0.0 to before 7.29.1 Fixed in 7.29.1 Patch available GHSA-r53p-7pc4-xj5r
- undici (npm) Vendor— Affected 8.0.0 to before 8.10.2 Fixed in 8.10.2 Patch available GHSA-r53p-7pc4-xj5r
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* | before 6.28.1; 7.0.0 to before 7.29.1; 8.0.0 to before 8.10.2 | Vulnerable | NodeJS |
- cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:* Versions before 6.28.1; 7.0.0 to before 7.29.1; 8.0.0 to before 8.10.2 Vulnerable ·NodeJS
Remediation
- Fix · CNA undici (undici) Fixed in 6.28.1, 7.29.1, 8.10.2
- Fix · GHSA-r53p-7pc4-xj5r undici (npm) Fixed in 6.28.1 Advisory →
- Fix · GHSA-r53p-7pc4-xj5r undici (npm) Fixed in 7.29.1 Advisory →
- Fix · GHSA-r53p-7pc4-xj5r undici (npm) Fixed in 8.10.2 Advisory →
Red Hat 3 advisories
- RHSA-2026:71017 Released 2026-09-23 · Red Hat rating ImportantRed Hat Hardened Images RPMs bug fix and enhancement update
- Red Hat Hardened Images nodejs24-1:24.21.0-1.hum1@aarch64, nodejs24-1:24.21.0-1.hum1@src, nodejs24-1:24.21.0-1.hum1@x86_64 +14
- RHSA-2026:66605 Released 2026-09-11 · Red Hat rating ImportantRed Hat Hardened Images RPMs bug fix and enhancement update
- Red Hat Hardened Images nodejs26-1:26.8.2-0.1.hum1@aarch64, nodejs26-1:26.8.2-0.1.hum1@src, nodejs26-1:26.8.2-0.1.hum1@x86_64 +14
- RHSA-2026:66008 Released 2026-09-09 · Red Hat rating ImportantRed Hat Hardened Images RPMs bug fix and enhancement update
- Red Hat Hardened Images grafana12.4-12.4.10-0.2.hum1@aarch64, grafana12.4-12.4.10-0.2.hum1@src, grafana12.4-12.4.10-0.2.hum1@x86_64
Fixed in the same release
Records fixed by the same vendor advisory or release, as the CNA lists them.
- Release ·
undici 6.28.1, 7.29.1, 8.10.2
3 records Highest priority Priority LOW 3 LOW
Other records, highest priority first
- TI-2026-15892 undici vulnerable to Denial of Service via unrequested WebSocket subprotocolPriority LOW 39
- TI-2026-58413 undici vulnerable to Denial of Service via unhandled error in WebSocket permessage-deflate decompressionPriority LOW 27
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Exploit Intelligence | Affected | No fix planned: Out of support scope |
| OpenShift Pipelines | Affected | No fix yet: Fix deferred |
| Red Hat AMQ Broker 7 | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Build of Podman Desktop | Affected | No fix yet: Fix deferred |
| Red Hat Developer Hub 1 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 10 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
| Red Hat Hardened Images | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Dev Spaces | Affected | No fix yet: Fix deferred |
| Red Hat Openshift Data Foundation 4 | Affected | No fix yet: Fix deferred |
| Red Hat Trusted Artifact Signer | Affected | No fix planned: Out of support scope |
| Secrets Management Console for Red Hat OpenShift | Affected | No fix planned: Out of support scope |
| Self-service automation portal 2 | Affected | No fix yet: Fix deferred |
| Red Hat Hardened Images | Fixed | RHSA-2026:66008, RHSA-2026:66605, RHSA-2026:71017 |
Not affected: 1 product
- Red Hat Hardened Images
Timeline
- 2026-10-02 Threatist record created from CVE-2026-18540
- 2026-10-03 Alias added: GHSA-r53p-7pc4-xj5r
- 2026-10-27 Affected versions changed · Red Hat
References
Advisory 3
Other 9
- https://github.com/nodejs/undici/commit/0160a719063fb0a77f4fdf9500b9166b91e14329
- https://github.com/nodejs/undici/commit/cd8af90b38ae33c2838d54a2d629774122effe95
- https://github.com/nodejs/undici/commit/ce31bc824b578008faae5d3350da66c1b5f71548
- https://hackerone.com/reports/3900104
- https://hackerone.com/reports/3900615
- https://github.com/nodejs/undici
- https://github.com/nodejs/undici/releases/tag/v6.28.1
- https://github.com/nodejs/undici/releases/tag/v7.29.1
- https://github.com/nodejs/undici/releases/tag/v8.10.2
More NodeJS Undici vulnerabilities
- TI-2026-01215 undici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') CVSS 3.1CRITICAL 9.8
- TI-2022-16376 `undici.request` vulnerable to SSRF using absolute URL on `pathname` CVSS 3.1CRITICAL 9.8
- TI-2023-09734 CRLF Injection in Nodejs ‘undici’ via host CVSS 3.1MEDIUM 6.5
- TI-2022-13193 CRLF injection in request headers CVSS 3.1MEDIUM 6.5
- TI-2022-16375 CRLF Injection in Nodejs ‘undici’ via Content-Type CVSS 3.1MEDIUM 5.3
- TI-2022-13194 Uncleared cookies on cross-host/cross-origin redirect in undici CVSS 3.1MEDIUM 6.5
Sources
- CVE-2026-18540 · CVE Program
- CVE-2026-18540 · NVD
- FIRST EPSS
- GHSA-r53p-7pc4-xj5r · GitHub Advisory Database · CC BY 4.0
- CVE-2026-18540 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences